| Brown rice protein,characterized by reasonable amino acid composition,high biological value and low sensitization,has high nutritional value.Germination can increase the contents of soluble protein,reduce the sugar,vitamins and minerals in brown rice,and produce functional factors,including gamma-aminobutyric acid(GABA)and inositol hexaphosphate(IP6).Although germinated brown rice has various health benefits,the solubility and stability of germinated brown rice protein(GBRP)are low,and it has not been well developed.In this paper,germinated brown rice protein-dextran conjugate(GBRP-Dex Con)was prepared by the wet method,which used germinated brown rice protein and dextran as the raw materials,and its structure and emulsifying properties were analyzed.The stability of GBRP-Dex Con in the emulsion was studied and it was used as an embedding medium to develop the microcapsule of probiotics.This article aims to provide a scientific basis for the comprehensive development and utilization of germinated brown rice protein(GBRP).The main findings were as follows:1.After the brown rice had been germinated for 35 hours,its protein contents reached the maximum,GBRP was extracted by alkali-soluble acid precipitation method,whose purity was 80.70%,whose yield rate was 4.78%and whose extraction rate was 51.01%.The prepared GBRP was suitable as the protein material for grafting reaction.When the grafting reaction of germinated brown rice protein and dextran was carried out,the effects of pH value,temperature and ratio of germinated brown rice protein to dextran on the degree of grafting(DG),emulsifying activity and emulsion stability of the GBRP-Dex Con were studied.The results showed that the DG of GBRP-Dex Con was positively correlated with pH value and temperature,and the DG reached the highest level when the mass ratio was 1:1.After the optimization of the response surface,the ratio of protein to dextran was 1:1,the pH value was 11.0 and the temperature was 96.0?,the maximum emulsification activity reached 1.15 and the emulsion stability reached 66.05,an increase of 21%and 92%respectively,compared with the emulsification activity and the emulsion stability of the original protein.2.The molecular structure of GBRP-Dex Con was studied to analyze the effects of glycosylation on the structure and physicochemical properties of GBRP,and discuss the mechanism of its improvement in functional properties.FTIR spectroscopy analysis showed that dextran was grafted with GBRP in the form of covalent bond;XRD analysis showed that the covalent binding between dextran and GBRP changed the crystal forms of dextran;SEM analysis showed that the protein particles of GBRP-Dex Con were uniformly fine and dispersedly attached to the lamellar structure of the dextran molecule.Compared with the original GBRP,the solubility of GBRP-Dex Con was increased by 10%(pH 7.0);The denaturation temperature of GBRP-Dex Con(122.2?)was 14.7? higher than that of GBRP(107.5?),and the thermal stability was improved;The emulsifying activity and the emulsion stability of GBRP-Dex Con were significantly higher than those of GBRP and common vegetable protein emulsifier(soy protein isolate);The DPPH-capturing ability and total reducing ability of GBRP-Dex Con increased more significantly(p<0.05)than those of GBRP.3.Plukenetia volubilis Linneo oil being used as the oil phase,different emulsions were prepared with the GBRP,GBRP-Dex Mix,GBRP-Dex Con,common vegetable protein emulsifier(soy protein isolate).The effects of emulsion particle size,physical stability,as well as different environmental factors(ionic strength,freeze-thaw,high temperature treatment)on the stability of the emulsion were studied,and the interface adsorption model of the emulsion was constructed.The results showed that the particle size of the emulsion prepared by GBRP-Dex Con was smaller than that of the control emulsion(p<0.05).When the concentration was 2%,the average minimum droplet diameter reached 0.483 ?m.Compared with all control groups,the emulsion prepared by GBRP-Dex Con had the best physical stability,good freeze-thaw stability,thermal stability and was not sensitive to high ionic strength,and therefore it can be used as an excellent emulsifier.4.Based on the excellent emulsifying and embedding properties of GBRP-Dex Con,the ability of GBRP-Dex Con of encapsulating probiotics was preliminarily studied with Bifidobacterium as core material.The results showed that the optimum volume ratio of wall material and core material was 8:1.Compared with spray-dried and unembedded processes,the Bifidobacterium microcapsules prepared by freeze-drying method had the smallest reduction in viability during the 16-week storage period,and the viable count reached 3.54×108 CFU/mL(storage temperature was 4?)and 6.85×106 CFU/mL(storage temperature was 25?).which was still able to reach the level of probiotics claim.Under heat treatment conditions of Bifidobacterium microcapsules at 85? for 30 min,the viable count was 7.34×106 CFU/mL which decreased by 2.50 logarithmic units,GBRP-Dex Con as microcapsule wall materials can improve the stability and survival rate of Bifidobacteria during thermal processing.5.The GBRP-Dex Con,used as the emulsifier,the ?-linolenic acid-rich Plukenetia volubilis Linneo oil,used as the source of fat,and other raw materials were compounded to develop a nutritious milk suitable for the general public,and a series of evaluations of the products were carried out.The results showed that the contents of protein,1 8 kinds of amino acids and a-linolenic acid in the nutritious milk were higher than those of breast milk and cow milk.The sensory characteristics of the nutritious milk were evaluated by an intelligent sensory evaluation device and compared with other competitive products on the market:The total contribution rate of PCA analysis for the Electronic Tongue was 95.06%.The bitterness,umami,richness and saltiness of the nutritious milk were at the lowest level,and the astringency was at the middle level.The Electronic Nose non-destructive testing technology was suitable for detecting and distinguishing nutritious milk.The total contribution rate of PCA analysis was 98.56%and the correct judgment rate of DFA analysis was 92.30%.SIMCA analysis showed that nutritious milk and enteral nutritious emulsion fell into the same category. |
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